Step 1 On medium high speed, cream butter and sugar until light and fluffy about 3 mins. Turn the mixer to high speed and add in egg mix well.
Step 2 Mix cocoa powder, red food coloring and vanilla to make a thick paste. Add to the batter and mix with medium speed till combined.
Step 3 Reduce the mixer to low speed and add in half of buttermilk then half of flour and mix till combined. Add the remaining buttermilk follows by the rest of flour. Use high speed to mix well.
Step 4 Reduce the mixer to low speed, add in salt, baking soda and vinegar. Turn to high speed and mix another couple minutes until completely combined.
Step 5 Divide the batter equally into the muffin pan lined with paper cases. Bake in the preheat oven 175C for 20-25 mins.
Step 6 For cream cheese frosting:
Using whisk attachment, whip the butter and cream cheese on high speed for 5 mins. Reduce the speed to low and slowly add in powdered sugar, mix till incorporated. Add in vanilla, mix to combine. Increase the mixer to medium high speed and whip for a few minutes until the frosting is light and fluffy. Use this to frost the cupcakes.